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Re: [paho-dev] C++ library submission

Thanks, Frank!

I'm not a C++ expert, but I will try to take a look shortly.

I'll file a CQ so that the Eclipse team can do an IP review on the code before we can accept it, and then post the information about it into Bugzilla.

Can you please also respond to the three questions I've added in the Bugzilla entry?

Really appreciate your willingness to contribute your code to the Paho project, and I'm sure folks like Ian will be happy to work with you and review how this works.


On Mon, May 27, 2013 at 5:43 PM, Frank Pagliughi <fpagliughi@xxxxxxxxxxxxxx> wrote:
Hey All,

I just uploaded the C++ wrapper library that I have been working on for the last few weeks:

As I mentioned in an earlier post, I wrapped the C library, and used the Java API as a guide. I literally cut and pasted the Javadoc from that project as the starting point for the C++ classes and documentation.

A few notes...

- I have only just discovered MQTT and used this library as a learning exercise. The submission represents everything I've ever done with MQTT to date, so it has yet to be used or tested in a production environment.

- I would appreciate any guidance on the direction to take the library in, as I plan to actually use it myself, and I will keep working on it.

- I chose to go with rather generic class names like "client" and "exception" in an "mqtt" namespace. I assume that I would generally keep the namespace closed and use the classes fully qualified, like "mqtt::client", etc.

- I tried to mimic the coding style of the C++ standard library. Class names in lower case with underscores, etc.

- I concentrated on the asynchronous library. In this version, the synchronous client (mqtt::client) just makes asynchronous calls and blocks until they complete.

- I used C++11 language and library extensions, particularly for shared pointers and portable thread synchronization objects. A recent compiler is required. I tested with GCC 4.6 and 4.7 on Linux.

- The dynamic objects (particularly messages and tokens) are intended to be allocated on the heap and accessed through shared pointers. The more static components (like clients and callback objects) can be declared globally or on the stack. This seemed a natural way to use the objects, but all of them can be created on the heap if the user wants complete consistency. All the classes define a shared pointer type with the extension "_ptr", like mqtt::message_ptr, mqtt::itoken_ptr, etc

- I used std::string to replace Java strings (not C-style char*) and std::vector for Java arrays. I've also assumed that a C++11 compiler would  provide move semantics for vectors so that returning them by value from a function does not have the performance hit that occurs when returning objects using earlier compilers (i.e. the object is moved out of the function rather than copied).

- Messages can use std::string for text data, but string objects can also be used for arbitrary binary data. In addition, the messages can be formed with a void* and a length.

- The exception hierarchy still needs some work.

- I haven't implemented any of the encryption or security features (yet).

Let me know what you think. Thanks.

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Andy Piper | Farnborough, Hampshire (UK)
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